Setting Up Ansible for AWS with Dynamic Inventory (EC2)

If your Ansible inventory fluctuates over time, with hosts spinning up and shutting down in response to business demands, the static inventory solutions described in Working with Inventory will not serve your needs. You may need to track hosts from multiple sources

Ansible integrates all of these options via a dynamic external inventory system. Ansible supports two ways to connect with external inventory: Inventory Plugins and inventory scripts.

If you use Amazon Web Services EC2, maintaining an inventory file might not be the best approach, because hosts may come and go over time, be managed by external applications, or you might even be using AWS autoscaling. For this reason, you can use the EC2 external inventory script.

You can use this script in one of two ways.

The easiest is to use Ansible’s -i command-line option and specify the path to the script after marking it executable:

1

ansible-iec2.py-uphoenix us-east-1d-mping

The second option is to copy the script to /etc/ansible/hosts and chmod +x it. You will also need to copy the ec2.ini file to /etc/ansible/ec2.ini. Then you can run ansible as you would normally.

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export AWS_ACCESS_KEY_ID='AK123'

export AWS_SECRET_ACCESS_KEY='abc123'

You can test the script by itself to make sure your config is correct:

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cd contrib/inventory

./ec2.py--list

After a few moments, you should see your entire EC2 inventory across all regions in JSON.

If you use Boto profiles to manage multiple AWS accounts, you can pass --profilePROFILE name to the ec2.py script.

You can then run ec2.py--profileprod to get the inventory for the prod account, although this option is not supported by ansible-playbook. You can also use the AWS_PROFILE variable – for example:

1

AWS_PROFILE=prodansible-playbook-iec2.pymyplaybook.yml

ec2.py

Python

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#!/usr/bin/env python

'''

EC2 external inventory script

=================================

Generates inventory that Ansible can understand by making API request to

AWS EC2 using the Boto library.

NOTE: This script assumes Ansible is being executed where the environment

variables needed for Boto have already been set:

export AWS_ACCESS_KEY_ID='AK123'

export AWS_SECRET_ACCESS_KEY='abc123'

Optional region environment variable if region is 'auto'

This script also assumes that there is an ec2.ini file alongside it. To specify a

different path to ec2.ini, define the EC2_INI_PATH environment variable:

export EC2_INI_PATH=/path/to/my_ec2.ini

If you're using eucalyptus you need to set the above variables and

you need to define:

export EC2_URL=http://hostname_of_your_cc:port/services/Eucalyptus

If you're using boto profiles (requires boto>=2.24.0) you can choose a profile

using the --boto-profile command line argument (e.g. ec2.py --boto-profile prod) or using

the AWS_PROFILE variable:

AWS_PROFILE=prod ansible-playbook -i ec2.py myplaybook.yml

For more details, see: http://docs.pythonboto.org/en/latest/boto_config_tut.html

You can filter for specific EC2 instances by creating an environment variable

named EC2_INSTANCE_FILTERS, which has the same format as the instance_filters

entry documented in ec2.ini. For example, to find all hosts whose name begins

with 'webserver', one might use:

export EC2_INSTANCE_FILTERS='tag:Name=webserver*'

When run against a specific host, this script returns the following variables:

- ec2_ami_launch_index

- ec2_architecture

- ec2_association

- ec2_attachTime

- ec2_attachment

- ec2_attachmentId

- ec2_block_devices

- ec2_client_token

- ec2_deleteOnTermination

- ec2_description

- ec2_deviceIndex

- ec2_dns_name

- ec2_eventsSet

- ec2_group_name

- ec2_hypervisor

- ec2_id

- ec2_image_id

- ec2_instanceState

- ec2_instance_type

- ec2_ipOwnerId

- ec2_ip_address

- ec2_item

- ec2_kernel

- ec2_key_name

- ec2_launch_time

- ec2_monitored

- ec2_monitoring

- ec2_networkInterfaceId

- ec2_ownerId

- ec2_persistent

- ec2_placement

- ec2_platform

- ec2_previous_state

- ec2_private_dns_name

- ec2_private_ip_address

- ec2_publicIp

- ec2_public_dns_name

- ec2_ramdisk

- ec2_reason

- ec2_region

- ec2_requester_id

- ec2_root_device_name

- ec2_root_device_type

- ec2_security_group_ids

- ec2_security_group_names

- ec2_shutdown_state

- ec2_sourceDestCheck

- ec2_spot_instance_request_id

- ec2_state

- ec2_state_code

- ec2_state_reason

- ec2_status

- ec2_subnet_id

- ec2_tenancy

- ec2_virtualization_type

- ec2_vpc_id

These variables are pulled out of a boto.ec2.instance object. There is a lack of

consistency with variable spellings (camelCase and underscores) since this

just loops through all variables the object exposes. It is preferred to use the

ones with underscores when multiple exist.

In addition, if an instance has AWS tags associated with it, each tag is a new

variable named:

- ec2_tag_[Key] = [Value]

Security groups are comma-separated in 'ec2_security_group_ids' and

'ec2_security_group_names'.

When destination_format and destination_format_tags are specified

the destination_format can be built from the instance tags and attributes.

The behavior will first check the user defined tags, then proceed to

check instance attributes, and finally if neither are found 'nil' will

be used instead.

'my_instance': {

'region': 'us-east-1', # attribute

'availability_zone': 'us-east-1a', # attribute

'private_dns_name': '172.31.0.1', # attribute

'ec2_tag_deployment': 'blue', # tag

'ec2_tag_clusterid': 'ansible', # tag

'ec2_tag_Name': 'webserver', # tag

...

}

Inside of the ec2.ini file the following settings are specified:

...

destination_format: {0}-{1}-{2}-{3}

destination_format_tags: Name,clusterid,deployment,private_dns_name

...

These settings would produce a destination_format as the following:

'webserver-ansible-blue-172.31.0.1'

'''

# (c) 2012, Peter Sankauskas

#

# This file is part of Ansible,

#

# Ansible is free software: you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by